The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
J T L Thong - One of the best experts on this subject based on the ideXlab platform.
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a robust focusing and Astigmatism Correction method for the scanning electron microscope
Scanning, 2006Co-Authors: J C H Phang, J T L ThongAbstract:This paper discusses a new approach to focusing and Astigmatism Correction based on the fast fourier transforms (FFTs) of scanning electron microscopy (SEM) images. From the FFTs, it is possible to obtain information on the severity of the defocus and Astigmatism. This information is then processed by an algorithm to perform real-time focusing and Astigmatism Correction on the SEM. The algorithm has been tested on defocused and astigmatic images of different samples, including those with highly directional features. Experiments show that the images obtained after running the algorithm can be as good as those that an experienced SEM operator can achieve.
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a robust focusing and Astigmatism Correction method for the scanning electron microscope part iii an improved technique
Scanning, 2006Co-Authors: J C H Phang, J T L ThongAbstract:As described in a previous work, a new technique has been developed to perform automatic focusing and Astigmatism Correction on any general scanning electron microscope (SEM) sample ranging from gold-on-carbon to integrated circuit (IC) tracks. In this work, various improvements made to this technique are reported. They include the implementation of direct control of the SEM and the development of three new algorithms, namely the adaptive fast Fourier transform (FFT) algorithm, the coarse focusing algorithm, and the fine focusing algorithm. Direct control reduces the communication time with the SEM while the three new algorithms are integrated with the existing technique to make it even more robust to noise and to extend it to correct images with any degree of defocus and Astigmatism. The enhanced focusing and Astigmatism Correction algorithm is able to perform the Correction in a shorter time while maintaining the accuracy of the original algorithm even under noisy conditions.
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A robust focusing and Astigmatism Correction method for the scanning electron microscope—Part III: An improved technique
Scanning, 2006Co-Authors: J C H Phang, J T L ThongAbstract:As described in a previous work, a new technique has been developed to perform automatic focusing and Astigmatism Correction on any general scanning electron microscope (SEM) sample ranging from gold-on-carbon to integrated circuit (IC) tracks. In this work, various improvements made to this technique are reported. They include the implementation of direct control of the SEM and the development of three new algorithms, namely the adaptive fast Fourier transform (FFT) algorithm, the coarse focusing algorithm, and the fine focusing algorithm. Direct control reduces the communication time with the SEM while the three new algorithms are integrated with the existing technique to make it even more robust to noise and to extend it to correct images with any degree of defocus and Astigmatism. The enhanced focusing and Astigmatism Correction algorithm is able to perform the Correction in a shorter time while maintaining the accuracy of the original algorithm even under noisy conditions.
J C H Phang - One of the best experts on this subject based on the ideXlab platform.
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a robust focusing and Astigmatism Correction method for the scanning electron microscope
Scanning, 2006Co-Authors: J C H Phang, J T L ThongAbstract:This paper discusses a new approach to focusing and Astigmatism Correction based on the fast fourier transforms (FFTs) of scanning electron microscopy (SEM) images. From the FFTs, it is possible to obtain information on the severity of the defocus and Astigmatism. This information is then processed by an algorithm to perform real-time focusing and Astigmatism Correction on the SEM. The algorithm has been tested on defocused and astigmatic images of different samples, including those with highly directional features. Experiments show that the images obtained after running the algorithm can be as good as those that an experienced SEM operator can achieve.
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a robust focusing and Astigmatism Correction method for the scanning electron microscope part iii an improved technique
Scanning, 2006Co-Authors: J C H Phang, J T L ThongAbstract:As described in a previous work, a new technique has been developed to perform automatic focusing and Astigmatism Correction on any general scanning electron microscope (SEM) sample ranging from gold-on-carbon to integrated circuit (IC) tracks. In this work, various improvements made to this technique are reported. They include the implementation of direct control of the SEM and the development of three new algorithms, namely the adaptive fast Fourier transform (FFT) algorithm, the coarse focusing algorithm, and the fine focusing algorithm. Direct control reduces the communication time with the SEM while the three new algorithms are integrated with the existing technique to make it even more robust to noise and to extend it to correct images with any degree of defocus and Astigmatism. The enhanced focusing and Astigmatism Correction algorithm is able to perform the Correction in a shorter time while maintaining the accuracy of the original algorithm even under noisy conditions.
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A robust focusing and Astigmatism Correction method for the scanning electron microscope—Part III: An improved technique
Scanning, 2006Co-Authors: J C H Phang, J T L ThongAbstract:As described in a previous work, a new technique has been developed to perform automatic focusing and Astigmatism Correction on any general scanning electron microscope (SEM) sample ranging from gold-on-carbon to integrated circuit (IC) tracks. In this work, various improvements made to this technique are reported. They include the implementation of direct control of the SEM and the development of three new algorithms, namely the adaptive fast Fourier transform (FFT) algorithm, the coarse focusing algorithm, and the fine focusing algorithm. Direct control reduces the communication time with the SEM while the three new algorithms are integrated with the existing technique to make it even more robust to noise and to extend it to correct images with any degree of defocus and Astigmatism. The enhanced focusing and Astigmatism Correction algorithm is able to perform the Correction in a shorter time while maintaining the accuracy of the original algorithm even under noisy conditions.
Javier Mendicute - One of the best experts on this subject based on the ideXlab platform.
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vector analysis of Astigmatism Correction after toric intraocular lens implantation
Journal of Cataract and Refractive Surgery, 2015Co-Authors: Eva Maria Krall, Javier Mendicute, E M Arlt, Melchior Hohensinn, Sarah Moussa, Gerlinde Jell, Jorge L Alio, Ana B Plazapuche, Lucia Bascaran, Gunther GrabnerAbstract:Purpose To determine astigmatic changes by vector analysis and postoperative refractive and visual outcomes after implantation of the monofocal aspheric bitoric AT Torbi 709M toric intraocular lens (IOL). Setting Three centers in Salzburg, Austria, and Alicante and San Sebastian, Spain. Design Prospective interventional case series. Methods Preoperative and postoperative visual acuity, subjective and objective refractions, and corneal radii using a topographer were examined in all patients. All patients had postoperative examinations within the first week and at 6 to 12 weeks. Astigmatic changes were evaluated using the Alpins vector method based on 3 fundamental vectors as follows: target induced Astigmatism (TIA), surgically induced Astigmatism (SIA), and difference vector. The various relationships between these 3 vectors were calculated, providing an extensive description of the astigmatic Correction achieved. Results Eighty-eight eyes (71 patients) were included. Postoperatively, refractive cylinder was reduced significantly ( P Conclusion Implantation of the toric IOL was safe and effective for the treatment of eyes with cataract in combination with preexisting regular corneal Astigmatism over a short-term follow-up. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.
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foldable toric intraocular lens for Astigmatism Correction in cataract patients
Journal of Cataract and Refractive Surgery, 2008Co-Authors: Javier Mendicute, Cristina Irigoyen, Jaime Aramberri, Ana Ondarra, Robert MontesmicoAbstract:Purpose To evaluate the results of AcrySof toric intraocular lens (IOL) (Alcon) implantation to correct preexisting Astigmatism in patients having cataract surgery. Setting Ophthalmology Service, Donostia Hospital, San Sebastian, Spain. Methods This prospective observational study included 30 eyes of 15 consecutive patients with more than 1.00 diopter (D) of preexisting corneal Astigmatism having cataract surgery. Bilateral implantation of the AcrySof toric IOL was performed after phacoemulsification. The uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere, residual keratometric and refractive cylinders, and toric IOL axis were measured. Results The UCVA was 20/40 or better in 93.3% of eyes and 20/25 or better in 66.6%. All eyes achieved 20/25 or better BCVA. The mean refractive cylinder decreased significantly after surgery from −2.34 D ± 1.28 (SD) to −0.72 ± 0.43 D (P Conclusions The results indicate that phacoemulsification and posterior chamber AcrySof toric IOL implantation is an effective option to correct preexisting Astigmatism in cataract surgery. The AcrySof toric IOL showed good rotational stability.
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foldable toric intraocular lens for Astigmatism Correction in cataract patients
Journal of Cataract and Refractive Surgery, 2008Co-Authors: Javier Mendicute, Cristina Irigoyen, Jaime Aramberri, Ana Ondarra, Robert MontesmicoAbstract:PURPOSE: To evaluate the results of AcrySof toric intraocular lens (IOL) (Alcon) implantation to correct preexisting Astigmatism in patients having cataract surgery. SETTING: Ophthalmology Service, Donostia Hospital, San Sebastian, Spain. METHODS: This prospective observational study included 30 eyes of 15 consecutive patients with more than 1.00 diopter (D) of preexisting corneal Astigmatism having cataract surgery. Bilateral implantation of the AcrySof toric IOL was performed after phacoemulsification. The uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere, residual keratometric and refractive cylinders, and toric IOL axis were measured. RESULTS: The UCVA was 20/40 or better in 93.3% of eyes and 20/25 or better in 66.6%. All eyes achieved 20/25 or better BCVA. The mean refractive cylinder decreased significantly after surgery from 2.34 D G 1.28 (SD) to 0.72 G 0.43 D (P<.01). Vector analysis of attempted versus achieved Correction showed that 100% of eyes were within G1.00 D and 80% and 93.9% were within G0.50 D for J0 and J45, respectively. The mean toric IOL axis rotation was 3.63 G 3.11 degrees, with rotation less than 10 degrees in 96.7% of eyes. CONCLUSIONS: The results indicate that phacoemulsification and posterior chamber AcrySof toric IOL implantation is an effective option to correct preexisting Astigmatism in cataract surgery. The AcrySof toric IOL showed good rotational stability.
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Foldable toric intraocular lens for Astigmatism Correction in cataract patients.
Journal of Cataract and Refractive Surgery, 2008Co-Authors: Javier Mendicute, Cristina Irigoyen, Jaime Aramberri, Ana Ondarra, Robert Montés-micóAbstract:PURPOSE: To evaluate the results of AcrySof toric intraocular lens (IOL) (Alcon) implantation to correct preexisting Astigmatism in patients having cataract surgery. SETTING: Ophthalmology Service, Donostia Hospital, San Sebastian, Spain. METHODS: This prospective observational study included 30 eyes of 15 consecutive patients with more than 1.00 diopter (D) of preexisting corneal Astigmatism having cataract surgery. Bilateral implantation of the AcrySof toric IOL was performed after phacoemulsification. The uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere, residual keratometric and refractive cylinders, and toric IOL axis were measured. RESULTS: The UCVA was 20/40 or better in 93.3% of eyes and 20/25 or better in 66.6%. All eyes achieved 20/25 or better BCVA. The mean refractive cylinder decreased significantly after surgery from 2.34 D G 1.28 (SD) to 0.72 G 0.43 D (P
Robert Montesmico - One of the best experts on this subject based on the ideXlab platform.
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foldable toric intraocular lens for Astigmatism Correction in cataract patients
Journal of Cataract and Refractive Surgery, 2008Co-Authors: Javier Mendicute, Cristina Irigoyen, Jaime Aramberri, Ana Ondarra, Robert MontesmicoAbstract:Purpose To evaluate the results of AcrySof toric intraocular lens (IOL) (Alcon) implantation to correct preexisting Astigmatism in patients having cataract surgery. Setting Ophthalmology Service, Donostia Hospital, San Sebastian, Spain. Methods This prospective observational study included 30 eyes of 15 consecutive patients with more than 1.00 diopter (D) of preexisting corneal Astigmatism having cataract surgery. Bilateral implantation of the AcrySof toric IOL was performed after phacoemulsification. The uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere, residual keratometric and refractive cylinders, and toric IOL axis were measured. Results The UCVA was 20/40 or better in 93.3% of eyes and 20/25 or better in 66.6%. All eyes achieved 20/25 or better BCVA. The mean refractive cylinder decreased significantly after surgery from −2.34 D ± 1.28 (SD) to −0.72 ± 0.43 D (P Conclusions The results indicate that phacoemulsification and posterior chamber AcrySof toric IOL implantation is an effective option to correct preexisting Astigmatism in cataract surgery. The AcrySof toric IOL showed good rotational stability.
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foldable toric intraocular lens for Astigmatism Correction in cataract patients
Journal of Cataract and Refractive Surgery, 2008Co-Authors: Javier Mendicute, Cristina Irigoyen, Jaime Aramberri, Ana Ondarra, Robert MontesmicoAbstract:PURPOSE: To evaluate the results of AcrySof toric intraocular lens (IOL) (Alcon) implantation to correct preexisting Astigmatism in patients having cataract surgery. SETTING: Ophthalmology Service, Donostia Hospital, San Sebastian, Spain. METHODS: This prospective observational study included 30 eyes of 15 consecutive patients with more than 1.00 diopter (D) of preexisting corneal Astigmatism having cataract surgery. Bilateral implantation of the AcrySof toric IOL was performed after phacoemulsification. The uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere, residual keratometric and refractive cylinders, and toric IOL axis were measured. RESULTS: The UCVA was 20/40 or better in 93.3% of eyes and 20/25 or better in 66.6%. All eyes achieved 20/25 or better BCVA. The mean refractive cylinder decreased significantly after surgery from 2.34 D G 1.28 (SD) to 0.72 G 0.43 D (P<.01). Vector analysis of attempted versus achieved Correction showed that 100% of eyes were within G1.00 D and 80% and 93.9% were within G0.50 D for J0 and J45, respectively. The mean toric IOL axis rotation was 3.63 G 3.11 degrees, with rotation less than 10 degrees in 96.7% of eyes. CONCLUSIONS: The results indicate that phacoemulsification and posterior chamber AcrySof toric IOL implantation is an effective option to correct preexisting Astigmatism in cataract surgery. The AcrySof toric IOL showed good rotational stability.
Joseph M. Maubach - One of the best experts on this subject based on the ideXlab platform.
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Derivative-free optimization for autofocus and Astigmatism Correction in electron microscopy
2020Co-Authors: Me Maria Rudnaya, R.m.m. Mattheij, Joseph M. MaubachAbstract:A simultaneous autofocus and two-fold Astigmatism Correction method for electron microscopy is described. The method uses derivative-free optimization in order to ??nd a global optimum of an image variance, which is an image quality measure. The Nelder-Mead simplex method and the Powell interpolation-based trust-region method are discussed and compared for an application running on a scanning transmission electron microscope.
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Autofocus and two-fold Astigmatism Correction in HAADF-STEM
2020Co-Authors: Me Maria Rudnaya, R.m.m. Mattheij, W Van Den Broek, R M P Doornbos, Joseph M. MaubachAbstract:A new simultaneous autofocus and two-fold Astigmatism Correction method is proposed for High Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM). The method makes use of a modification of an image variance, which has already been used before as an image quality measure for different types of microscopy. In this paper we describe numerical simulations based on a classical HAADF-STEM linear image formation model showing that the modified variance reaches it's maximum for Scherzer focus and zero Astigmatism. In order to find this maximum in a three-parameter space we employ the well-known Nelder-Mead simplex optimization algorithm. The method is implemented and tested on a FEI Tecnai F20.It successfully finds the optimal defocus and zero Astigmatism with the time and accuracy, compared with the human operator. The method is iterative, and finding the optimal defocus and zero Astigmatism requires obtaining typically 20-50 images.
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Orientation identification of the power spectrum
2020Co-Authors: Me Maria Rudnaya, R.m.m. Mattheij, Joseph M. MaubachAbstract:The image Fourier transform is widely used for defocus and Astigmatism Correction in electron microscopy. The shape of a power spectrum (the square of a modulus of image Fourier transform) is directly related to the three microscope’s controls, namely defocus and two-fold (two-parameter) Astigmatism. In this paper the new method for power spectrum orientation identification is proposed. The method is based on the three measures which are related to the microscope’s controls. The measures are derived from the mathematical moments of the power spectrum. The method is tested with the help of a Gaussian benchmark, as well as with the scanning electron microscopy experimental images. The method can be used as an assisting tool for increasing the capabilities of defocus and Astigmatism Correction a of non-experienced scanning electron microscopy user, as well as a basis for automated application.
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Orientation identification of the power spectrum
Optical Engineering, 2011Co-Authors: Me Maria Rudnaya, R.m.m. Mattheij, Joseph M. Maubach, Hennie G. Ter MorscheAbstract:The image Fourier transform is widely used for defocus and Astigmatism Correction in electron microscopy. The shape of a power spectrum (the square of a modulus of image Fourier transform) is directly related to the three microscope controls, namely, defocus and twofold (two-parameter) Astigmatism. We propose a new method for power-spectrum orientation identification. The method is based on the three measures that are related to the microscope's controls. The measures are derived from the mathematical moments of the power spectrum and is tested with the help of a Gaussian benchmark, as well as with the scanning electron microscopy experimental images. The method can be used as an assisting tool for increasing the capabilities of defocus and Astigmatism Correction a of nonexperienced scanning electron microscopy user, as well as a basis for automated application.
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defocus and twofold Astigmatism Correction in haadf stem
Ultramicroscopy, 2011Co-Authors: Me Maria Rudnaya, R.m.m. Mattheij, W Van Den Broek, R M P Doornbos, Joseph M. MaubachAbstract:A new simultaneous autofocus and twofold Astigmatism Correction method is proposed for High Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM). The method makes use of a modification of image variance, which has already been used before as an image quality measure for different types of microscopy, but its use is often justified on heuristic grounds. In this paper we show numerically that the variance reaches its maximum at Scherzer defocus and zero Astigmatism. In order to find this maximum a simultaneous optimization of three parameters (focus, x- and y-stigmators) is necessary. This is implemented and tested on a FEI Tecnai F20. It successfully finds the optimal defocus and Astigmatism with time and accuracy, compared to a human operator.
